National Institute of Sport

Paris, France

National Institute of Sport

Paris, France
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Meur Y.L.,National Institute of Sport | Hausswirth C.,National Institute of Sport | Natta F.,National Institute of Sport | Couturier A.,National Institute of Sport | And 2 more authors.
Journal of Applied Physiology | Year: 2013

In sport, high training load required to reach peak performance pushes human adaptation to their limits. In that process, athletes may experience general fatigue, impaired performance, and may be identified as overreached (OR). When this state lasts for several months, an overtraining syndrome is diagnosed (OT). Until now, no variable per se can detect OR, a requirement to prevent the transition from OR to OT. It encouraged us to further investigate OR using a multivariate approach, including physiological, biomechanical, cognitive, and perceptive monitoring. Twenty-four highly trained triathletes were separated into an overload group and a normo-trained group (NT) during 3 wk of training. Given the decrement of their running performance, 11 triathletes were diagnosed as OR after this period. A discriminant analysis showed that the changes of eight parameters measured during a maximal incremental test could explain 98.2% of the OR state (lactatemia, heart rate, biomechanical parameters and effort perception). Variations in heart rate and lactatemia were the two most discriminating factors. When the multifactorial analysis was restricted to these variables, the classification score reached 89.5%. Catecholamines and creatine kinase concentrations at rest did not change significantly in both groups. Running pattern was preserved and cognitive performance decrement was observed only at exhaustion in OR subjects. This study showed that monitoring various variables is required to prevent the transition between NT and OR. It emphasized that an OR index, which combines heart rate and blood lactate concentration changes after a strenuous training period, could be helpful to routinely detect OR. Copyright © 2013 the American Physiological Society.

Plews D.J.,High Performance Sport New Zealand | Laursen P.B.,High Performance Sport New Zealand | Le Meur Y.,National Institute of Sport | Hausswirth C.,National Institute of Sport | And 2 more authors.
International Journal of Sports Physiology and Performance | Year: 2014

Purpose: To establish the minimum number of days that heart-rate- variability (HRV, ie, the natural logarithm of square root of the mean sum of the squared differences between R-R intervals, Ln rMSSD) data should be averaged to achieve correspondingly equivalent results as data averaged over a 1-wk period. Methods: Standardized changes in Ln rMSSD between different phases of training (normal training, functional overreaching (FOR), overall training, and taper) and the correlation coefficients of percentage changes in performance vs changes in Ln rMSSD were compared when averaging Ln rMSSD from 1 to 7 d, randomly selected within the week. Results: Standardized Ln rMSSD changes (90% confidence limits, CL) from baseline to overload (FOR) were 0.20 0.28, 0.33 ± 0.26, 0.49 0.33, 0.48 0.28, 0.47 0.26, 0.45 0.26, and 0.43 0.29 on days 1 to 7, respectively. Correlations (90% CL) over the same time sequence and training phase were -.02 .23, -.07 .23, -.17 ± .22, -.25 .22, -.26 .22, -.28 .21, and -.25 .22 on days 1 to 7. There were almost perfect quadratic relationships between standardized changes/r values vs the number of days Ln rMSSD was averaged (r2 = .92 and .97, respectively) in trained triathletes during FOR. This indicates a plateau in the increase in standardized changes/r values' magnitude after 3 and 4 d, respectively, in trained triathletes. Conclusion: Practitioners using HRV to monitor training adaptation should use a minimum of 3 (randomly selected) valid data points per week. © 2014 Human Kinetics, Inc.

Rabita G.,National Institute of Sport | Dorel S.,University of Nantes | Slawinski J.,Paris West University Nanterre La Défense | Saez-de-Villarreal E.,Pablo De Olavide University | And 3 more authors.
Scandinavian Journal of Medicine and Science in Sports | Year: 2015

The objective of this study was to characterize the mechanics of maximal running sprint acceleration in high-level athletes. Four elite (100-m best time 9.95-10.29s) and five sub-elite (10.40-10.60s) sprinters performed seven sprints in overground conditions. A single virtual 40-m sprint was reconstructed and kinetics parameters were calculated for each step using a force platform system and video analyses. Anteroposterior force (FY), power (PY), and the ratio of the horizontal force component to the resultant (total) force (RF, which reflects the orientation of the resultant ground reaction force for each support phase) were computed as a function of velocity (V). FY-V, RF-V, and PY-V relationships were well described by significant linear (mean R2 of 0.892±0.049 and 0.950±0.023) and quadratic (mean R2=0.732±0.114) models, respectively. The current study allows a better understanding of the mechanics of the sprint acceleration notably by modeling the relationships between the forward velocity and the main mechanical key variables of the sprint. As these findings partly concern world-class sprinters tested in overground conditions, they give new insights into some aspects of the biomechanical limits of human locomotion. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Aubry A.,National Institute of Sport | Hausswirth C.,National Institute of Sport | Louis J.,National Institute of Sport | Coutts A.J.,University of Technology, Sydney | Le Meur Y.,National Institute of Sport
Medicine and Science in Sports and Exercise | Year: 2014

PURPOSE: The purpose of this study is to examine whether performance supercompensation during taper is maximized in endurance athletes after experiencing overreaching during an overload training (OT) period. METHODS: Thirty-three trained male triathletes were assigned to either OT (n = 23) or normal training groups (n = 10, CTL) during 8 wk. Cycling performance and maximal oxygen uptake (V̇O2max) were measured after 1 wk of moderate training, a 3-wk period of OT, and then each week during 4-wk taper. RESULTS: Eleven of the 23 subjects from the OT group were diagnosed as functionally overreached (F-OR) after the overload period (decreased performance with concomitant high perceived fatigue), whereas the 12 other subjects were only acutely fatigued (AF) (no decrease in performance). According to qualitative statistical analysis, the AF group demonstrated a small to large greater peak performance supercompensation than the F-OR group (2.6% ± 1.1%) and the CTL group (2.6% ± 1.6%). V̇O2max increased significantly from baseline at peak performance only in the CTL and AF groups. Of the peak performances, 60%, 83%, and 73% occurred within the two first weeks of taper in CTL, AF, and OR, respectively. Ten cases of infection were reported during the study with higher prevalence in F-OR (70%) than that in AF (20%) and CTL (10%). CONCLUSION: This study showed that 1) greater gains in performance and V̇O2max can be achieved when higher training load is prescribed before the taper but not in the presence of F-OR; 2) peak performance is not delayed during taper when heavy training loads are completed immediately prior; and 3) F-OR provides higher risk for training maladaptation, including increased infection risks. © 2014 by the American College of Sports Medicine.

Rabita G.,National Institute of Sport | Slawinski J.,National Institute of Sport | Girard O.,Research and Education Center | Bignet F.,French Federation of Triathlon | Hausswirth C.,National Institute of Sport
Medicine and Science in Sports and Exercise | Year: 2011

PURPOSE: The aims of this study were i) to evaluate changes in leg-spring behavior during an exhaustive run in elite triathletes and ii) to determine whether these modifications were related to an increase in the energy cost of running (Cr). METHODS: Nine elite triathletes ran to exhaustion on an indoor track at a constant velocity corresponding to 95% of the velocity associated with the maximal oxygen uptake (mean ± SD = 5.1 ± 0.3 m·s, time to exhaustion = 10.7 ± 2.6 min). Vertical and horizontal ground reaction forces were measured every lap (200 m) by a 5-m-long force platform system. Cr was measured from pulmonary gas exchange using a breath-by-breath portable gas analyzer. RESULTS: Leg stiffness (-13.1%, P < 0.05) and peak vertical (-9.2%, P < 0.05) and propulsive (-7.5%, P < 0.001) forces decreased significantly with fatigue, whereas vertical stiffness did not change significantly. Leg and vertical stiffness changes were positively related with modifications of aerial time (R = 0.66, P < 0.01 and R = 0.72, P < 0.01, respectively) and negatively with contact time (R = 0.71, P < 0.01 and R = 0.74, P < 0.01, respectively). Alterations of vertical forces were related with the decrease of the angle of velocity vector at toe off (R = 0.73, P < 0.01). When considering mean values of oxygen uptake, no change was observed from 33% to 100% of the time to exhaustion. However, between one-third and two-thirds of the fatiguing run, negative correlations were observed between oxygen consumption and leg stiffness (R = 0.83, P < 0.001) or vertical stiffness (R = 0.50, P < 0.03). CONCLUSIONS: During a constant run to exhaustion, the fatigue induces a stiffness adaptation that modifies the stride mechanical parameters and especially decreases the maximal vertical force. This response to fatigue involves greater energy consumption. © 2011 The American College of Sports Medicine.

Hausswirth C.,National Institute of Sport | Louis J.,National Institute of Sport | Aubry A.,National Institute of Sport | Bonnet G.,University of Paris 13 | And 2 more authors.
Medicine and Science in Sports and Exercise | Year: 2014

PURPOSE: This study aimed to examine whether (i) objective markers of sleep quantity and quality are altered in endurance athletes experiencing overreaching in response to an overload training program and (ii) potential reduced sleep quality would be accompanied with a higher prevalence of upper respiratory tract infections in this population. METHODS: Twenty-seven trained male triathletes were randomly assigned to either overload (n = 18) or normal (CTL, n = 9) training groups. Respective training programs included a 1-wk moderate training phase followed by a 3-wk period of overload or normal training, respectively, and then a subsequent 2-wk taper. Maximal aerobic power and oxygen uptake (V̇O 2max) from incremental cycle ergometry were measured after each phase, whereas mood states and incidences of illness were determined from questionnaires. Sleep was monitored every night of the 6 wk using wristwatch actigraphy. RESULTS: Of the 18 overload training group subjects, 9 were diagnosed as functionally overreached (F-OR) after the overload period, as based on declines in performance and V̇O2max with concomitant high perceived fatigue (P < 0.05), whereas the other 9 overload subjects showed no decline in performance (AF, P > 0.05). There was a significant time-group interaction for sleep duration (SD), sleep efficiency (SE), and immobile time (IT). Only the F-OR group demonstrated a decrease in these three parameters (-7.9% ± 6.7%,-1.6% ± 0.7%, and-7.6% ± 6.6% for SD, SE, and IT, respectively, P < 0.05), which was reversed during the subsequent taper phase. Higher prevalence of upper respiratory tract infections were also reported in F-OR (67%, 22%, and 11% incidence rate for F-OR, AF, and CTL, respectively). CONCLUSION: This study confirms sleep disturbances and increased illness in endurance athletes who present with symptoms of F-OR during periods of high volume training. © 2014 by the American college of Sports Medicine.

Hausswirth C.,National Institute of Sport | Le Meur Y.,National Institute of Sport
Sports Medicine | Year: 2011

Gender-based differences in the physiological response to exercise have been studied extensively for the last four decades, and yet the study of post-exercise, gender-specific recovery has only been developing in more recent years. This review of the literature aims to present the current state of knowledge in this field, focusing on some of the most pertinent aspects of physiological recovery in female athletes and how metabolic, thermoregulatory, or inflammation and repair processes may differ from those observed in male athletes.Scientific investigations on the effect of gender on substrate utilization during exercise have yielded conflicting results. Factors contributing to the lack of agreement between studies include differences in subject dietary or training status, exercise intensity or duration, as well as the variations in ovarian hormone concentrations between different menstrual cycle phases in female subjects, as all are known to affect substrate metabolism during sub-maximal exercise. If greater fatty acid mobilization occurs in females during prolonged exercise compared with males, the inverse is observed during the recovery phase. This could explain why, despite mobilizing lipids to a greater extent than males during exercise, females lose less fat mass than their male counterparts over the course of a physical training programme.Where nutritional strategies are concerned, no difference appears between males and females in their capacity to replenish glycogen stores; optimal timing for carbohydrate intake does not differ between genders, and athletes must consume carbohydrates as soon as possible after exercise in order to maximize glycogen store repletion. While lipid intake should be limited in the immediate post-exercise period in order to favour carbohydrate and protein intake, in the scope of the athletes general diet, lipid intake should be maintained at an adequate level (30). This is particularly important for females specializing in long-duration events. With protein balance, it has been shown that a negative nitrogen balance is more often observed in female athletes than in male athletes. It is therefore especially important to ensure that this remains the case during periods of caloric restriction, especially when working with female athletes showing a tendency to limit their caloric intake on a daily basis.In the post-exercise period, females display lower thermolytic capacities than males. Therefore, the use of cooling recovery methods following exercise, such as cold water immersion or the use of a cooling vest, appear particularly beneficial for female athletes. In addition, a greater decrease in arterial blood pressure is observed after exercise in females than in males. Given that the return to homeostasis after a brief intense exercise appears linked to maintaining good venous return, it is conceivable that female athletes would find a greater advantage to active recovery modes than males.This article reviews some of the major gender differences in the metabolic, inflammatory and thermoregulatory response to exercise and its subsequent recovery. Particular attention is given to the identification of which recovery strategies may be the most pertinent to the design of training programmes for athletic females, in order to optimize the physiological adaptations sought for improving performance and maintaining health. © 2011 Adis Data Information BV. All rights reserved.

Louis J.,University of Nice Sophia Antipolis | Louis J.,National Institute of Sport | Hausswirth C.,National Institute of Sport | Easthope C.,University of Nice Sophia Antipolis | Brisswalter J.,University of Nice Sophia Antipolis
European Journal of Applied Physiology | Year: 2012

The purpose of this study was to test the effect of a 3-week strength training program of knee extensor muscles on cycling delta efficiency in master endurance athletes. Nine master (age 51.5 ± 5.5 years) and 8 young (age 25.6 ± 5.9 years) endurance athletes with similar training levels participated in this study. During three consecutive weeks, all the subjects were engaged in a strength training program of the knee extensor muscles. Every week, they performed three training sessions consist of 10 × 10 knee extensions at 70% of maximal repetition with 3 min rest between in a leg extension apparatus. Maximal voluntary contraction torque (MVC torque) and force endurance (End) were assessed before, after every completed week of training, and after the program. Delta efficiency (DE) in cycling was evaluated before and after the training period. Before the training period, MVC torque, End, and DE in cycling were significantly lower in masters than in young. The strength training induced a significant improvement in MVC torque in all the subjects, more pronounced in masters (+17.8% in masters vs. +5.9% in young, P < 0.05). DE in cycling also significantly increased after training in masters, whereas it was only a trend in young. A significant correlation (r = 0.79, P < 0.01) was observed between MVC torque and DE in cycling in masters. The addition of a strength training program for the knee extensor muscles to endurance-only training induced a significant improvement in strength and cycling efficiency in master athletes. This enhancement in muscle performance alleviated all the age-related differences in strength and efficiency. © 2011 Springer-Verlag.

Pournot H.,National Institute of Sport | Pournot H.,University of Nice Sophia Antipolis | Bieuzen F.,National Institute of Sport | Louis J.,University of Nice Sophia Antipolis | And 2 more authors.
PLoS ONE | Year: 2011

The objectives of the present investigation was to analyze the effect of two different recovery modalities on classical markers of exercise-induced muscle damage (EIMD) and inflammation obtained after a simulated trail running race. Endurance trained males (n = 11) completed two experimental trials separated by 1 month in a randomized crossover design; one trial involved passive recovery (PAS), the other a specific whole body cryotherapy (WBC) for 96 h post-exercise (repeated each day). For each trial, subjects performed a 48 min running treadmill exercise followed by PAS or WBC. The Interleukin (IL) -1 (IL-1), IL-6, IL-10, tumor necrosis factor alpha (TNF-α), protein C-reactive (CRP) and white blood cells count were measured at rest, immediately post-exercise, and at 24, 48, 72, 96 h in post-exercise recovery. A significant time effect was observed to characterize an inflammatory state (Pre vs. Post) following the exercise bout in all conditions (p<0.05). Indeed, IL-1β (Post 1 h) and CRP (Post 24 h) levels decreased and IL-1ra (Post 1 h) increased following WBC when compared to PAS. In WBC condition (p<0.05), TNF-α, IL-10 and IL-6 remain unchanged compared to PAS condition. Overall, the results indicated that the WBC was effective in reducing the inflammatory process. These results may be explained by vasoconstriction at muscular level, and both the decrease in cytokines activity pro-inflammatory, and increase in cytokines anti-inflammatory. © 2011 Pournot et al.

Kudo S.,University of Otago | Vennell R.,University of Otago | Wilson B.,National Institute of Sport
Journal of Biomechanics | Year: 2013

This study describes the effect of hand acceleration on hydrodynamic forces acting on the human hand in angular and general motions with variable hand accelerations. Even if accelerations of a swimmer's hand are believed to have an important role in generating hydrodynamic forces on the hand, the effect of accelerations in angular and general motions on hydrodynamic forces on the swimmers hand has not been previously quantified. Understanding how hand acceleration influences force generation can provide useful information to enhance swimming performance. A hand-forearm model attached to a tri-axial load cell was constructed to measure hydrodynamic forces acting only on the hand when the model was rotated and accelerated in a swimming flume. The effect of acceleration on hydrodynamic forces on the hand was described by comparing the difference between accelerating and non-accelerating hands in different flow conditions. Hydrodynamic forces on the accelerating hand varied between 1.9 and 10 times greater than for the non-accelerating hand in angular motion and varied between 1.7 and 25 times greater than for the non-accelerating hand in general motion. These large increases occurred not only during positive acceleration phases but also during negative acceleration phases, and may be due to the added mass effect and a vortex formed on the dorsal side of the hand. This study provides new evidence for enhanced stroke techniques in swimming to generate increased propulsion by changing hand velocity during a stroke. © 2013 Elsevier Ltd.

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